1. Field of the Invention
The present invention relates to a laser diode drive signal processor and a method for driving a laser diode, which are applicable to, for example, an optical disk apparatus for accessing a phase change type optical disk. The present invention further relates to the realization of driving a laser diode with decreased consumption power by supplying a first driving current according to a signal level of an alternating current component of a driving signal for driving the laser diode, and by supplying a second driving current according to a signal level of an error signal compared to the driving signal by detecting the light amount of a laser beam, and further by adding those first and second driving currents to drive the laser diode.
2. Description of the Related Art
In a conventional optical disk apparatus for accessing a phase change type optical disk, a laser diode emits a laser beam and focuses the beam on the optical disk. A returning beam reflected on the a phase change type optical disk is received and a receiving result of the returning beam is processed to reproduce data recorded on the optical disk.
On the other hand, when the conventional optical disk apparatus records data on the optical disk, the apparatus switches a laser beam emitting period between a first period for intermittently raising the light amount of the laser beam and irradiating the optical disk and a second period for irradiating the optical disk with a fixed light amount of the laser beam in accordance with the data to be recorded, and thereby the conventional optical disk apparatus forms sequential marks and spaces on an information recording surface of the optical disk to record desired data on the optical disk in this way.
Incidentally, this kind of optical disk apparatus can increase the recording density by shortening the wavelength of the laser beam. For achieving this, accessing the optical disk with a laser beam having a wavelength of, for example, 500 nm, on the contrary of the wavelength from 650 nm to 780 nm of the laser beam used by the conventional optical disk apparatus at the time of accessing the optical disk, would make it possible to increase the recording density by the difference of the wavelength.
However, a laser diode for emitting such a short wavelength laser beam generally has a large resistance value, and it is thus required to raise a driving voltage necessary for driving such a short wavelength type laser diode by the difference in the resistance value, compared with the conventional long wavelength type laser diode. As a result, an optical disk apparatus equipped with such short wavelength type laser diode has to raise the voltage of its power supply.
Hence, such conventional optical disk apparatus has a problem that its driving circuit increases its consumption power. Further high power and high speed driving device id very expensive.
The present invention is made from the consideration to such a problem, and aims to propose a laser diode drive signal processor and a method for driving a laser diode that are capable of driving the laser diode with lowered consumption power.
According to a first aspect of the present invention, there is provided a laser diode drive signal processor for driving a laser diode to be used to emit a laser beam for accessing an optical information recording medium with the laser beam. The processor comprises alternating current side driving current supply means for supplying a first driving current according to a signal level of an alternating current component; light amount detecting means coupled to the laser diode for detecting a light amount of the laser beam; error signal generating means for generating an error signal based on the detected light amount of the laser beam and a reference signal; direct current side driving current supply means for supplying a second driving current according to a signal level of the error signal; adding means for adding the first driving current from the alternating current side driving current supply means and the second driving current from the direct current side driving current supply means to generate a third driving current; and supply means for supplying the third driving current composed of the first and second driving currents to the laser diode.
The laser diode drive signal processor according to the first aspect of the present invention can decrease its consumption power because the first driving current according to the signal level of the alternating current component does not include a direct current component and thereby the first driving current can be obtained from a lower power-supply voltage.
According to a second aspect of the invention, there is provided a method for driving a laser diode to be used to emit a laser beam for accessing an optical information recording medium with the laser beam. The method comprises the steps of supplying a first driving current according to a signal level of an alternating current component; detecting a light amount of the laser beam; generating an error signal based on the detected light amount of the laser beam and a reference signal; supplying a second driving current according to a signal level of the error signal; adding the first driving current and the second driving current to generate a third driving current; and supplying the third driving current composed of the first and second driving currents to the laser diode.
The method for driving a laser diode according to the second aspect of the present invention can similarly decrease the consumption power of an optical disk apparatus to which the method is applied, because the first driving current according to the signal level of the alternating current component does not include a direct current component and thereby the first driving current can be supplied from a lower power-supply voltage.